Electrical contact between two substrates, such as a motherboard 100 and a daughter card 102 shown in FIG. 1, can be established using a connector system 104. The connector system 104 may comprise a header connector 106 mounted on the daughter card 102, and a receptacle connector 108 mounted on the motherboard 100. For example, as shown in FIG. 1, the daughter card 102 may be oriented horizontally, and the motherboard 100 may be oriented vertically. The receptacle connector 106 therefore is suspended from the motherboard 100 by the connections between the receptacle connector 108 and the motherboard 100.
The receptacle connector 108 can be the primary (or the only) structure for supporting the header connector 106 and the daughter card 102. The connections between the receptacle connector 108 and the motherboard 100 thus can function as the primary or sole support for the header connector 106 and the daughter card 102. As the daughter card 102 can weigh up to several pounds, this type of mounting arrangement can subject the connections between the receptacle connector 108 and the motherboard 100 to substantial stresses.
The stresses induced by the weight of the daughter card 102 and the header connector 106 can have a detrimental effect on the connections between the receptacle connector 108 and the motherboard 100. This problem can be particularly troublesome in applications where the receptacle connector 108 is surface mounted, i.e., where the receptacle connector 108 is mounted on a mounting surface 100a of the motherboard 100 using solder connections (such as in a ball-grid array connector). Subjecting a solder connection to substantial levels of stress and thermal cycling can weaken the solder connection, and can lead to cracking and premature failure thereof. Such degradation can potentially reduce the reliability and the useful life of the connector system.
One known solution to the aforementioned problem is to configure the receptacle connector 106 with a strain relief post that protrudes into the motherboard. However, this solution is not without detriment. First, the receptacle should be able to float or move relative to the motherboard during reflow of the receptacle connector onto the motherboard. A strain relief post, which is inserted into a hole in the motherboard, can inhibit the movement of the receptacle connector during reflow. This restraint of movement can cause stress in post-reflow solder connections and prevent proper alignment of the receptacle connector contacts and the corresponding solder pads or vias. Second, even if the hole defined by the motherboard is supersized to allow play between the strain relief post and an inner surface of the strain relief hole, the post itself must contact the inner surface at some point to carry shear force to the motherboard. Therefore, a solderable strain relief post may be needed. This adds to the cost of the components and the process.
Another known solution is to attach guide pins to the motherboard and guide pin receiving receptacles on the daughtercard. This is usually a four part assembly that takes up valuable board real estate on the motherboard and the daughtercard and often requires mechanical attachment of the guide pins/guide pin receiving receptacles to the respective boards via an externally threaded shaft and an internally threaded nut. Again, this adds cost and takes up valuable space on the PCBs.